Children with specific language impairment (SLI) and children with auditory processing disorder (APD) often present with poor skills in expressive and/or receptive language and reading. Given the overlap in behavioral symptoms between APD and SLI, clinicians and researchers are faced with an important question. Is APD a construct that is theoretically and practically distinct from SLI? The answer to this question has important implications for the assessment and treatment of children with oral and written language difficulties. The long-term goal of this research is to determine if and how SLI and APD can be distinguished. In the proposed study, children with SLI and children with APD will be compared on behavioral measures of receptive and expressive language, reading, verbal and visual working memory, nonverbal cognitive processing, motor skills, and auditory processing of speech and nonspeech stimuli. The clinical groups will be identified by speech-language pathologists and audiologists, so that we may understand how the diagnostic classifications made by practitioners relate to performance on the test battery. Discriminant function analysis will be used to determine which variables best discriminate children with SLI and children with APD. In addition, cluster analysis will be used to determine whether the sample can best be characterized as consisting of two, three, or more groups, and if these groups correspond to the diagnostic classifications. The results of this study will provide descriptive data regarding the performance of children with SLI and APD on a wide range of linguistic and nonlinguistic tasks, data regarding characteristics which distinguish children with SLI and APD, and data regarding the best way to categorize children with SLI and APD. The results will form the foundation for further research employing larger, more stringently selected samples and both behavioral and electrophysiological measures.